Means for making flexible metal hose



Jan. 7-,1947. K. H. EVE RT MEANS FOR MAKING FLEXIBLE METAL HOSE Original Filed June 16, 1941 3 Sheets-Sheet 1 I I H H H Jan. 7, 1947.

K H. EVERT MEANS FOR MAKING FLEXIBLE METAL HOSE 3 Sheets-sheet 2 Original Filed June 16, 1941 M M Z W @2 5 W Z 7 5 a 7 w 2 v2 f 1 a 4 6 K m 5 J i A l y W 4, 5 j Z. i 7.4 1 0. 7 z z 1 i j g 1111 d. W T Q U 5Q. a 4 P y a Xv w a m c. 4

Jan. 7, 1947. k, H, EVERT 2,413,816

MEANS FOR MAKING FLEXIBLE METAL HOSE 3 Sheetssheaf 5 Original Filed June 16, 1941 mnmmu flay/6782 07;-

Patented Jan. 7, 1947 MEANS FOR MAKING FLEXIBLE METAL HOSE Karl H. Evert, Elmhurst, Ill.

Original application June 16, 1941, Serial No. No. 2,313,329, dated March d this application January 9, 1943, Serial No. 471,863

398,272, now Patent 1943. Divided an 12 Claims.

The present invention relates to means for making flexible metal hose or metallic flexible conduits.

Metal conduits or hoses of this type are formed from preformed metallic strips helically wound in a suitable rotating device whereby the adjacent edge portions of the convolutions of the strip are joined, as by brazing or otherwise, to effect a seam. The finished conduit is longitudinally corrugated in shape.

The present invention comprehends a novel device for producing a novel metal hose or condui I run the strip of metal through a suitable forming or profiling device, not specifically shown, so that the strip is formed with a U- shaped profile with laterally extending edge flanges at the open end of the U, and also generally curving the profiled strip to approximately the curvature of the mandrel upon which the profiled and curved strip is to be wound.

Then, according to my invention, the strip passes between one or more novel rollers and the novel mandrel, the latter being a smooth surfaced cylindrical mandrel free of any projections or ribs or the like, along which smooth surface the coils or convolutions of the conduit will slide.

The roller or rollers are so located as to posit1on the adjacent convolutions in given spaced relation whereby the adjacent flanges will overlap for joining. These flanges are at the base of the helical trough formed between the convolutions, and located against or adjacent the smooth cylindrical surface of the mandrel, preferably at the locus of first contact of the profiled strip with the mandrel as the strip initially becomes associated with the mandrel.

Other rollers may be used and located at difierent points around the mandrel So as to guide the movement of the convolutions around the mandrel. These rollers may be spaced from the mandrel so that the convolutions will not touch the mandrel but will spacedly encircle it. In such case the axial movement or feed of the convolutions relative to the mandrel will be greatly facilitated, with practically no friction nor resistance.

Preferably, one of the discs, such as the lead disc, is designed to weld the overlapping adjacent flanges. By welding at a point where the profiled strip initially contacts the mandrel then the convolutions are fixed in relation and will turn about and slide along the mandrel as a single unitary corrugated tube.

An important novel feature is the welding at the base of the trough between the adjacent convolutions, that is, adjacent to the surface of the mandrel. This welding forms a continuous seam between the overlapping flanges and for the full Width of the overlapping portions of such flanges.

The invention also comprehends as a part thereof the provision of novel means for gathering the convolutions, that is, spacing the coils or convolutions closer together for the finished profile of the coil or conduit fed from the mandrel. This novel means comprises a roller or rollers which stress the coils or convolutions to make them gather closer together. In doing so the outer diameter is increased, the inner diameter remaining the same, that is, approximately that of the outside diameter of the mandrel.

Other objects, advantages, capabilities, features, and the like are comprehended by the invention as will later appear and as are inherently possessed by the invention.

This is a division of my copending application Serial No. 398,272 filed June 16, 1941, now Patent No. 2,313,329, issued March 9, 1943.

Referring to the drawings:

Fig. 1 is a conventional side view of a machine embodying the invention;

Fig. 2 is a transverse view, on an enlarged scale, with parts in section, of the invention;

Fig. 3 is a fragmentary side view, on a. further enlarged scale, of the invention;

Fig. 4 is a diagram howing the advantage of welding an inner seam;

Figs. 5 and 6 are fragmentary sectional views of different kinds of rollers used in the invention;

Fig. '7 is a fragmentary and transverse sectional view taken in a plane represented by line 5- in Fig. 1 of the drawings;

Fig. 8 is a fragmentary part sectional and part side view developed from planes represented by lines 3-8 in Fig. 7 of the drawings;

Figs. 9, 10, ll, 12 and 13 are fragmentary sectional views of different types of rollers used in the invention;

Figs. 14 and 15 are part transverse views and part end views of the invention showing the novel means for driving the rollers about the tube; and,

Fig. 16 is a fragmentary view for illustration of the drive means for a roller.

Referring more in detail to the drawings, for illustratin the invention, the preformed or p filed strip l is helically wound upon a mandrel 2 having a smooth cylindrical outer surface upon which the strip is wound and along which the tube slides axially to be fed off to a take-up means. The mandrel is axially stationary but preferably .strip, I cent flange A of the preceding convolution of the rotates at the same or faster angular speed as or than the tube, yet the invention comprehends the use of a mandrel which may not rotate. In the latter case as the tube turns over the mandrel, there would be a little more friction between the tube and the mandrel but that would not be suificient to affect the efiicient production of the tube in accordance with my invention. Suitable lubrication can be used between the mandrel and the tube if desired or found necessary.

The tube is made from metal strips, such as stainless steel, or the like, The strip is forced through any suitable preforming or profiling device (not shown) to give therstrip the desired cross-sectional form or profile,.and.-longitudinal curve to wind around themandrel.

In the present invention it is preferable to profile the strip in U-shape with the bendof the U forming the outer crest 3 of the strip, and with the legs of the U formed with lateral flanges d and 5 which when united constitute apart of the inner trough between adjacent convolutions of the profiled stripwhen helically wound on' the mandrel 2. As the strip is helically wound on the mandrel one'of'the fiangessuch as flange t, will lie in contact with the surface of the mandrel, as at the top, as shown, and the other'fiange, such as flange 5 of the succeeding convolution of the will lie upon-and in contact with the adjastrip, These overlapping'flanges' arewelded together as hereinafter described.

It is preferable tohave these fianges'overlap along a narrow width where the welded seam is produced so that there will be no fissure between the overlapping portions of the flanges on either ing device passes to the mandrel the first roller or rollers will correctly position or direct such convolution axially relative to the previously formed convolution; the second and third rollers, as rollers la and 8, will hold such adjacent convolutions properly spaced, and the fourth roller, as roller 9, will guide the convolution into their helical paths for axial feed of the tube along the mandrel in the direction of the arrow shown in Fig. 3.

One of these rollers may be a welding roller, such as roiler in. In such case the body of the roller 'willbe composed of electrically insulating material and will include a central metal or car- ,bon disc i2 (see'Fig. 6) constituting one of the welding electrodes, for conduction of the electrical energy for welding at the periphery i3 while applying pressure to the flanges and i, the mandrel i constituting the other of the welding electrodes.

The rollers may be or" the form' shown inFigs. i0 and 11, which are useful when workingwith strips having high altitude convolutions. In this case each roller may have a pair of grooves H5 and to with an intermediate annular pressing periphery it for functioning in the trough between adjacent convolutions for maintaining proper spacing or spread and for pressor both sides of the welding trace, and also for economy wherein strips of'less width may be used than washeretofore required, when bonding by solder or by brazing.

The strip is helically wound upon or about the outer cylindrical surface of the mandrel as the strip is fed out of'the preforming or profiling device and moved in between the mandrel and a series of rollers I, la, 8 and 3 (conventionally shown in Fig. 2) having suitable profiled peripheries'conforming to the inter-profiles of the convolutions of the strip. These rollers are rotatable about respective axes generally parallel with the axis of the mandrel and the tube but normal to the circumferential portions of the convolutions contacted thereby, and are distributed around I the mandrel, besides being-progressively axially spaced in accordance with the pitch of the helically wound strip. These rollers are principally for holding the convolutions of the strip properly spaced, and for pressing against the overlapping flanges i and 5 to efiect a correct welding of such flanges, as later explained.

These rollers may be of simple form as shown in Figs. 2, 3 and 5, preferably composed of insulating material (although that is not wholly ecessary) more or less in disc form and with a tapered periphery id, to easily enter between con volutions of the strip, and for pressing periphery ii, The thickness of these rollers gauges the spread or spacing of such convolutions. The periphery ii of the roller l presses against the flange ito hold it in contact with the mandrel,

and. the periphery ll of the roller 5a presses 1mg the'fianges thereorfl'and with lateral rims H and it so spaced as to span the adjacent convolutions, and to contactthe opposite remote sides of the adjacent convolutions, as shown in Fig. 10. By such means the profile of the convolutions is maintained, beside keeping themproperly spaced for the welding function to be performed.

Any of these rollers may act as the welding electrode. In such case thebody of the roller serving as the welding electrode (see Fig. 11) will be made of electrically non-conducting material i9, and include a centra1 metalor carbon disc 2! tocarry the currenigthe welding being effected at the periphery 2| of such disc.

In the case of using the type of roller shown in Fig. 11, in such a position as shown at la in Fig. 2, the use of other roll rs atipositions '8 and 9 in Fig. 2 would not be necessary; ecause the roller at position la would perform all the functions ful to hold the tube substantially, coaxial vor central with the mandrel. After the strips are welded they will wind or turn about the mandrel together as a unit. All that would be necessary when starting the winding of the strip would be to direct, in any suitable manner, the initial end of the profiled strip intov a curved path around the mandrel for the first convolution to the point where it becomes welded to the next convolution. After that the strip will wind perfectly about the mandrel as the adjacent convolutions which are welded together proceed in helical path from the point of welding.

The welding is eii'ected electrically between the contacting points of the rotary electrode and the mandrel. The desired number of electrical energy impulses foragiven unit'of length of the line of welding or welding trace may be used. This relation may be'so'chosen that the welding spots will so overlap that there willbe a substantially continuous welded seam between the flanges 5 and 3 whereby the tube will be fluidtight, and the widthof the welded seam will be suflicient to avoid fissures between the flanges at the edges of the flanges.

If it were assumed that the welding took place along the helical line of the crest 3 of the convolutions with impulses of the value 2' for a given unit it of length along such line, the weld spots would be equal to 1' times u. Assuming the diameter D of the tube at the trough to be 2a and the diameter D at the crest 3 to be 3a, the circumference C of the former would be 26611' and the circumference C of the latter would be 3cm, or in the proportion of 2 to 3. Hence, by welding along the helical trough line instead of along the helical crest line, the work can be speeded up 50%. That is, for obtaining in spots along the helical trough line per unit of time the tube can be rotated 50% faster and fed on the mandrel 50% faster. To increase production 50% in this kind of work is immense and not a matter that would be apparent from the methods and means previously used.

As the profiled strip is wound on the mandrel 2 it travels in screw-fashion, that is, the tube rotates about the axis of the mandre1 and also progresses axiallydn proportion to the pitch of the helical form of the convolutions and the speed of rotation. This may be called the feed-off from the rolls.

The strip may have tWo or more U-shaped portions between the side flanges. In Fig. 12 the strip is shown with two U-shaped portions to and 3b between the side flanges 4a and 4b, and in Fig. 13 the strip is shown with three U-shaped portions 3a, 3b and 30 between flanges 4a and 4b. In such cases rollers lb and lcfor guiding and placing the convolutions would be used as shown in Figs. 12 and 13. The disc part of such roller pressing the adjacent flanges db and 4a together would act as the welding roller to weld such flanges together.

The disc electrodes shown in Figs. 6 and 11, corresponding to the disc electrode |2a shown in Figs. 12 and 13, may have an enlarged rim iZb as shown in section in Fig. 12. Any or all of the electrodes may use such rim when and where desired. In such case the sides of the peripheral portions of the rollers will be more sharply tapered or bevelled so as to leave suificient insulating air spaces at both sides of the enlarged rim 82b. See Fig. 12.

Along the feed-oil? path of the tube it is desirable to compress the convolutions. See Figs. '7 and 8. This may be effected by the use of compressing rollers 22, 23 and 2 3. These rollers may be of the general form shown in Fig, 3, but thinner and more closely axially spaced. They also are preferably rotatable on axes, which are at a normal to the convolutions being compressed, and are suitably arranged angularly about the tube, whereby two adjacent rollers may have overlapping portions between which a convolution of the tube may be axially squeezed or compressed.

As for example, when convolution 25 passes between rollers 22 and 23 it is given a decreased axial dimension and increased outward radial dimension, as shown in Fig. 8. When the convolution 26 passes between rollers 23 and 24, it is further decreased in axial dimension and increased in outward radial dimension, as shown in Fig. 8. More rollers may be used to still further compress the convolutions and increase their "outer diameters. The inner diameter of the con volutions remains the same because of the trough portions bearing on the surface of the mandrel 2. If the metal used is thin and has a tendency to 6 be weak then the roller 22, 23 and 24 may be of the form as roller 2'! shown in Fig. 9, which roller has compressing and supporting rims 28 and 29 at each side of the convolution to be axially compressed.

It is preferable that the rollers be driven. In Fig. 14 is shown means for driving the rollers as shown in Figs. 2 and 3, and in Fig. 15 is shown means for driving the rollers as shown in Figs. 7 and 8. In both cases the drive means is of generally annular form to surround the rollers to be driven and to be clear of the tube and the mandrel.

In both cases the driving means is shown as having an annular driving ring 2? having inner teeth 28 and rotatably supported between rollers or idlers 2B. Meshing with the teeth 28 are spiral gears 30 (see particularly Fig. 16) fixed to shafts 3! leading and secured to rollers I, la, 8 and 9 (see Figs. 14 and Figs. 2 and 3) and to rollers 22, 23 and 24 (see Figs. 7 and 8, and Fig. 15). The annular gear 21 may be rotated by a suitable driving gear 32. The shafts 3i are at an angle to the axis of the annular gear 2'! and at a normal to the convolutions to be acted upon by the rollers I, la, 8 and 9, and 22, 23 and 24 as the case may be.

As the tube now feeds off it may be taken-up by a suitable take-on device and wound on a suitable wind-up spool or reel.

While I have herein described and upon the drawings shown illustrative embodiments of my invention it is to be understood that the invention is not limited thereto but eomprehends other constructions, arrangements of parts. details, features, and the like, without departing from the spirit of the invention.

Having thus disclosed the invention, I claim:

1. In a machin for forming a flexible tube from a preformed bendable Weldable strip undulated in transverse section to include a crest and opposed wall portions and also including flanges projecting laterally outwardly r spectively from the unclosed edges of said wall portions,

; a rod-like mandrel having a free smooth cylindrical surface, means for feeding said strip generally transversely of and tangentially onto said smooth surface of said mandrel with the strip crest portion radially outermost therefrom and the flanges thereof upon said surface of the mandrel, and guide means for guiding said strip into a spiral formation about and upon said surface of said mandrel with one flange of each convolution in overlapping relation with the other flange in the next preceding convolution upon said surface of said mandrel, said guide including guide roller means including disc-like portions rotatable about axes directed generally lengthwise or the mandrel but diagonally thereof, said disc-like portions being spaced lengthwise of the mandrel with edge portions proximate thereto to engage with the opposed wall portions of a plurality of said convolutions for controlling their spacing axially of the mandrel and hence the pitch of the spiral formation and for pressing against said overlapped flanges to hold the latter against said surface, and electrode means ineluding said mandrel for welding the overlapping flanges together While said flanges are held against said surface of said mandrel.

2. In a machine for forming a flexible tube from a preformed bendable strip generally undulated in transverse section, a rod-like mandrel having a free smooth cylindrical surface, and means for guiding and shaping the strip helically onto and about said smooth surface of the mandrel comprising a plurality of roller members having disc portions distributed along a path directed helically about said mandrel, said disc portions being disposed with circumferential edge portions thereof proximate to the said free smooth periphery of said mandrel at their respective positions in the helical path and with side portions thereof for contacting opposite sides of the helically wound strip to control the spacing of the convolutions thereof, and means for rotating said members about their principal axes in the direction to advance said circumferential edge portions in the same direction with respect to said path.

3. In a machine for forming a flexible tube from a preformed bendable weldable strip undulated in transverse section to include opposed wall portions, a crest bridging such wall portions and flanges projecting laterally outwardly respectively from the unclosed edges of said Wall portions, a rod-like mandrel having a free smooth cylindrical surface, and guide means for guiding said strip into a spiral formation upon and about said smooth surface of said mandrel with one flange in each convolutionin overlapping rela tion with the other flange in the next preceding convolution and upon said free smooth cylindrical surface of said mandrel, said guide means including means for projecting inwardly of said convolutions to engage the strip side walls therein for preventing simple axial movement of the formation but to cause screw-like advancement thereof when the same isrotated about the mandrel, and a guide roller disposed with a diametric element generally perpendicularly to the mandrel, said roller having an end wall adjacently to the mandrel and in a plane diagonal thereto in opposed spaced relation with said inwardly projecting means axially of the mandrel to guide said strip onto the mandrel in position to add onto the last-formed convolution While said inwardly projecting means stabilizes the formation on the mandrel.

4. In a machine for forming a flexible tube from a preformed bendable strip undulated in transverse section to include a crest and opposed side walls, a rod-like mandrel having a free smooth cylindrical surface, and means for guiding and propelling said strip helically onto and about said smooth surface of the mandel, comprising a roller having a groove circumscribing its circular periphery, said roller being disposed with such periphery adj acently to the mandrel to press said strip upon said free smooth surface.

of the mandrel and with its principal axis slightly diagonally of the mandrel to place a portion of the roller groove in position to receive the crest and side Walls at a portion of such a strip directed helically upon and about the mandrel, said roller being rotatable about its principal axis, and the side wall of the groove therein being adapted to grip the strip side wall portions therein wherefore to advance said strip helically about the mandrel pursuant to such rotation.

5. The combination set forth in claim 4, but wherein the roller contains a plurality of such peripheral grooves axially spaced a distance to receive strip side wall portions in adjacent convolutions of the helically formed strip.

6. In a machine for forming a flexible tube from a preformed bendable weldable strip undulated in transverse section to include a crest and opposed side walls and also including flanges projecting laterally outwardly respectively from the unclosed edges of said walls, a rod-like mandrel, and guide means for guiding said strip into a spiral formation about said mandrel with the strip crest radially outwardly and with one flange of each convolution in overlapping relation in given extent less than the width of the flanges with the other flange on the next preceding convolution, said guide means including guide roller means including disc-like portions spaced axially of the mandrel and with peripheral edge portions proximate to the mandrel and their principal axes directed generally axially of the mandrel but diagonally thereof whereby said disc-like portions engage with opposed side wall portions in a plurality of said convolutions, said disc-like portions being sufliciently close to the mandrel to engage and press the overlapping flanges between their peripheral edges and the mandrel and being rotatable to advance the spiral formation screwlike about and along the mandrel, and at least one of said disc-like portions comprising an electrode element including an annular portion extending about the periphery thereof to contact one of the overlapping flanges, and a layer of insulating material about the sides of said electrode element to prevent contact thereof with the side Walls of the strip.

7. In a machine for forming a flexible tube from a preformed bendable weldable strip undulated in transverse section to include a crest and opposed side Walls and also including flanges projecting laterally outwardly respectively from the unclosed edges of said walls, a rod-like mandrel having a smooth cylindrical surface, and guide means for guiding said strip into a spiral formation about said surface of said mandrel with the strip, crest radially outwardly and with one flange of each convolution in overlapping relation with the other flange on the next preceding convolution, convolution compressing means including a plurality of compressing rollers having disc-like portions spaced variantly axially of the mandrel and with peripheral portions extending at opposite sides of the convolution at such axial distance apart as to axially compress and axially bodily move the portion of the convolution between said peripheral portions for reducing the Width of the convolution and increasing its diameter and for gathering the convolutions in closer proximity.

8. In a machine for forming a flexible tube from a preformed bendable weldable strip undulated in transverse section to include a crest and opposed side walls and also including flanges projecting laterally outwardly respectively from the unclosed edges of said walls, a rod-like mandrel having a smooth cylindrical surface, and guide means for guiding said strip into a spiral formation about said surface of said mandrel with the strip crest radially outwardly and with one flange of each convolution in overlapping relation with the other flange on the next preceding convolution, convolution compressing means including a plurality of compressing rollers having disc-like portions spaced variantly axially of the mandrel and with peripheral portions extending at opposite sides of the convolution. at such axial distance apart as to axially compress and axially bodily move the portion of the convolution between said peripheral portions for reducing the width of the convolution and increasing its diameter and for gathering the convolutions in closer proximity, and driving means for driving said compressing means.

9. In a machine. for forminga flexible tube from a preformed bendable weldable strip of helical form and having an undulated transverse section to include a crest and opposed wall portions and also including flanges projecting laterally outwardly respectively from the unclosed edges of said wall portions; a cylindrical mandrel about which said preformed strip is fed with the flanges thereof overlying the surface of said mandrel, means for guiding said strip helically around said mandrel with the strip crest portion radially outermost therefrom and with a flange of a convolution of the strip overlapping a flange of an adjacent convolution of the strip for part of the extent of the width of the overlapping flanges and with th inner of said flanges being throughout the width thereof in contact with said mandrel, said guide means including a disc-like roller having a peripheral portion with side walls for contacting the opposing side Walls of the adjacent convolutions of the strip to maintain said convolutions in given spaced relation and said overlapping flanges in given overlapped relation and also having a peripheral edge portion for pressing against the outer of said overlapping flanges to maintain them in close contact and with the inner flange in close contact with the surface of said mandrel, said roller at its peripheral edge portion having an electrode for passing of an clectrio current through said flanges to said mandrel to effect a resistance weld of the flanges.

10. In a machine for forming a flexible tube from a preformed bendable weldable strip of helical form and having an undulated transverse section to include a crest and opposed wall portions and also including flanges projecting laterally outwardly respectively from the unclosed edges of said wall portions; a cylindrical mandrel about which said preformed strip is fed with the flanges thereof overlying the surface of said mandrel, means for guiding said strip helically around said mandrel with the strip crest portion radially outermost therefrom and with a flange of a convolution of the strip overlapping a flange of an adjacent convolution of the strip for part of the extent of the width of the overlapping flanges and with the inner of said flanges being throughout the width thereof in contact with said mandrel, said guide means including a disc-like roller having a peripheral portion with side walls of electrically insulating material for contacting the opposing side walls of the adjacent convolutions of the strip to maintain said convolutions in given spaced relation and said overlapping flanges in given overlapped relation and also having a peripheral edge portion of electrically conducting material for pressing against the outer of said overlapping flanges to maintain them in close contact and with the inner flange in close contact with the surface of said mandrel, said conducting material being for the passing of electric current through said flanges to said mandrel to effect a resistance weld of the flanges.

11. In a machine for forming a flexible tube from a preformed bendable weldable strip of helical form and having an undulated transverse section to include a crest and opposed wall portions and also including flanges projecting laterally outwardly respectively from the unclosed edges of said wall portions; a cylindrical mandrel about which said preformed strip is fed with the flanges thereof overlying the surface of said mandrel, means for guiding said strip helically around said mandrel with the strip crest portion radially outermost therefrom and with a flange of a convolution of the strip overlapping a flange of an adjacent convolution of the strip for part of the extent of the width of the overlapping flanges and with the inner of said flanges being throughout the width thereof in contact with said mandrel, said guide means including a disc-like roller having a peripheral portion with side walls of electrically insulating material for contacting the opposing side walls of the adjacent convolutions of the strip to maintain said convolutions in given spaced relation and said overlapping flanges in given overlapped relation peripheral edge portion for pressing against the outer of said overlapping flanges to maintain them in close contact and with the inner flange in close contact with the surface of said mandrel, said roller at its peripheral edge portion having an electrode for passing of an electric current through said flanges to said mandrel to effect a resistance weld of the flanges.

12. In a machine for forming a flexible tube from a preformed bendable weldable strip of helical form and having an undulated transverse section to include a crest and opposed wall portions and also including flanges projecting laterally outwardly respectively from the unclosed edges of said wall portions; a cylindrical mandrel about which said preformed strip is fed with the flanges thereof overlying the surface of said mandrel, means for guiding said strip helically around said mandrel with the strip crest portion radially outermost therefrom and with a flange of a convolution of the strip overlapping a flange of an adjacent convolution of the strip for part of the extent of the width of the overlapping flanges and with the inner of said flanges being throughout the width thereof in contact with said mandrel, said guide means including a disc-like roller having a peripheral portion with side walls of electrically insulating material for contacting the opposing side walls of the adjacent convolutions of the strip to maintain said convolutions in given spaced relation and said overlapping flanges in given overlapped relation and of a width substantially equal to the width of the overlapping portions of said flanges for pressing against the outer of said overlapping flanges to maintain them in close contact and with the inner flange in close contact with the surface of said mandrel, said conducting material being for the passing of electric current through said flanges to said mandrel to effect a resistance weld of the flanges.

KARL H. EVERT.

and also having a 

